Sedimentary rocks of the world's oldest.

Komiya Associate Professor of the University of Tokyo (geology) and others found in the northeastern part of Canada, the world's oldest deposition formed 3.9 billion 60 million years ago (volume) rock. And that is obtained important clues old 130 million years at least than the previous record, to clarify the global environment of the time when primitive life was born.
Sifted this year from 2011, to investigate the Labrador region of the Canadian far northeast, Komiya Associate Professor and colleagues collected iron ore exposed on the surface of the earth. It was found the oldest sedimentary rocks in the dating of rock (to write) granite that was mixed inside. I seen such as minerals precipitated on the sea floor and has resulted from hardened.
From sedimentary rocks of 3.8 billion 30 million years ago, carbon of biological origin that are traces of the earliest form of life have been found in Greenland in the neighborhood. Carbon has also been detected from the rock of this time, I will have to rewrite the history of life birth if biological origin.
The originally, the Earth was born 4.6 billion years ago and was covered in a sea of ​​magma, I found this rock and was able to soon land is born. The world's oldest rocks are the metamorphic rocks of 4 billion 30 million years ago was found in northwestern Canada.
Sedimentary rocks formed at the surface of the earth is able to explore the environment of life at birth unlike metamorphic rock made ​​of the Earth's interior, but old does not remain almost crustal movement. Komiya associate professor talking "to clarify the place of birth life, I want to shed light on the dark ages" he said. I want to hope that the elucidation of the mystery of life birth progresses.


３９億６千万年以上前に形成された世界最古の堆積（たいせき）岩を、東大の小宮准教授（地質学）らがカナダ北東部で発見した。従来の記録より少なくとも１億３千万年古く、生命が誕生したころの原始の地球環境を解明する重要な手掛かりが得られるという。
　小宮准教授らは平成２３年から今年にかけ、カナダ最北東のラブラドル地方を調査し、地表に露出した鉄鉱石を採取。内部に混入した花崗（かこう）岩の年代測定で最も古い堆積岩と分かった。海底に沈殿した鉱物などが固まってできたとみられる。
　近隣のグリーンランドでは３８億３千万年前の堆積岩から、最古の生命の痕跡とされる生物由来の炭素が見つかっている。今回の岩からも炭素が検出されており、生物由来であれば生命誕生の歴史を塗り替えることになる。
　約４６億年前に誕生した地球は当初、マグマの海に覆われていたとされ、今回の岩は陸地が生まれて間もなくできたとみられる。世界最古の岩石はカナダ北西部で見つかった４０億３千万年前の変成岩とされる。
　地球の表面で形成される堆積岩は、地球内部でできた変成岩と違って生命誕生時の環境などを探ることができるが、地殻変動で古いものはほとんど残っていない。小宮准教授は「生命誕生の場を解明し、暗黒の時代に光を当てたい」と話している。生命誕生の謎の解明が進むことを期待したいですね。